Ultrafiltration Research Articles

Vibrio neptunius-ULV11 cell-free supernatant as a promising antifouling approach in reverse osmosis systems

One of the most common problems observed in continuous operation of desalination plants, is the presence of biofouling in ultrafiltration (UF) modules and reverse osmosis membranes (ROMs), decreasing permeated water obtention and increasing energy consumption among other adverse effects. To solve this problem, desalination industry applied UF modules and ROMs cleaning procedures that aims to increase half-life operation time, however, many of the actual cleaning procedures are focused on the addition of chemical compounds that provokes secondary effects such as UF modules and ROMs disintegration leading to structural changes and a decrease in plant performance. Thus, new approaches to replace current cleaning compounds with new ecofriendly and less secondary effects technologies are necessary.In this study, we present a Vibrio neptunius strain ULV11 isolate, with a high capacity to remove fouling in RO systems. In detail, ULV11 cell-free supernatant (CFS) was used in replace of chemical agents as a cleaning solution according to standard operational protocol on 3-year-old membranes of continuous operation. The results showed that CFS can be used under operational conditions (such high pressure and flux) allowed us to recover permeate volumes similar to those observed in traditional chemical treatment with better conductivity. This recovery was accompanied by a reestablishment of membrane topology observed by atomic force microscopy and EPS remotion since concanavalin A signal trough confocal microscopy was decrease as compared with biofouling control.

Development of zwitterion-functionalized graphene oxide/polyethersulfone nanocomposite membrane and fouling evaluation using solutes of varying charges

Abstract This study explores the functionalization of polyethersulfone (PES) ultrafiltration (UF) membranes using zwitterion-functionalized graphene oxide (GO) and assesses their interactions with solutes of different charges, both neutral and anionic. Initially, PES nanocomposite membranes were synthesized, incorporating varying dosages (ranging from 0-1 % (w/w)) of glycine-functionalized graphene oxide (Gly/GO) and diglycine-functionalized graphene oxide (diGly/GO) through a direct blending method. The physicochemical properties, including hydrophilicity, surface morphology, and porosity of these membranes were characterized using sessile-drop contact angle, tabletop scanning electron microscopy (SEM), and gravimetric methods, respectively. Subsequently, the antifouling performance of these synthesized membranes was assessed by exposing them to a solution containing sucrose as a neutral model foulant and humic acid as an anionic foulant. The incorporation of zwitterion-functionalized graphene oxide nanoparticles improved the surface wettability of the nanocomposite membrane, enhancing its resistance to sucrose fouling. This was supported by a reduction in flux declination ratio (e.g., 40.6 % for pristine PES, 29.7 % for 1.0 % (w/w) Gly/GO PES, and 33.1 % for 1.0 % (w/w) diGly/GO PES) and an increase in flux recovery ratio (67.2 % for pristine PES, 79.7 % for 1.0 % (w/w) Gly/GO PES, and 80.0% for 1.0 % (w/w) diGly/GO PES). The improvement in antifouling characteristics is attributed to the formation of a hydration layer on the membrane surface, which inhibits sucrose deposition. However, zwitterion-functionalized PES nanocomposite membranes displayed a higher affinity for anionic humic acid, resulting in a substantial flux decline and a lower flux recovery ratio. Overall, this research provides insights into the roles of surface wettability and the charge interactions between solutes and the membrane surface, both of which are crucial factors in determining fouling severity and the restorability of spent membranes.

Zwitterionic nanospheres engineered co-polymer composite membrane for precise protein-protein separation via dynamic self-assembly micelle deposition

The accurate protein-protein separation is important but technically challenging. Achieving such a precise separation using membrane requires the selective channels with appropriate pore geometry structure and high anti-fouling property. In this study, polyethersulfone-b-poly(sulfobetaine methyl methacrylate) (PES-b-PSBMA) was synthesized and engineered onto polysulfone (PSF) ultrafiltration (UF) membrane to fabricate zwitterionic nanospheres engineered co-polymer (ZN-e-CoP) composite membrane via dynamic self-assembly micelle deposition. On the one hand, self-assembly zwitterionic nanospheres were used as blocks to construct hydrophilic layers with size-dependent sieving channels, endowing ZN-e-CoP composite membranes with enhanced permselectivity and protein-protein separation abilities, meanwhile zwitterionic groups from nanospheres reinforced the structure stability of nanospheres/nanospheres and nanospheres/membrane via multiple intermolecular interactions. On the other hand, zwitterionic nanospheres can induce to produce the hydration layer enveloping themselves by binding water molecules, where hydration layer acts as a protective barrier on the membrane surface, impeding the protein adhesion. Hence, ZN-e-CoP_1a composite membrane exhibited superior separation properties with Lysozyme/Bovine Serum Albumin (BSA) separation factor of 18.1 and 95.4 % rejection against BSA, 10.1 and 2.3 times, respectively, higher these of pristine PSF membrane (1.8 and 42.1 %), without obviously sacrificing water flux. Simultaneously, hydration layer enables the ZN-e-CoP_1a membrane with enhanced anti-fouling performance and durability during the long-term operations. The proposed approach opens new pathways to fabricate excellent anti-fouling membranes for precise protein-protein separation.

Evaluation of the potential ultrafiltration to improve the quality of secondary effluents in tertiary treatment and reuse

Unsatisfactory effluent purification, limited to secondary treatment, considerably restricts the reuse of treated water. In this study, the performance of three ceramic ultrafiltration (UF) membranes UF1 (0.02 μm), UF2 (0.05 μm), and UF3 (0.1 μm) was evaluated for the recovery of secondary effluent (SE) from a wastewater treatment plant (WWTP) in Kenitra. The effects of different parameters on treated water quality were assessed, including transmembrane pressure (TMP), circulation velocity (CV), and membrane pore size. The results indicated that the UF1 membrane was more effective than UF2 and UF3, achieving maximum removal rates for chemical oxygen demand (COD), biochemical oxygen demand at 5 days (DBO5), and total suspended solids (TSS) of 75%, 72%, and 96%, respectively, under optimal operating conditions of TMP at 1 bar and CV at 1 m/s. UF2 achieved removal rates of 70%, 71%, and 94% for COD, BOD5, and TSS, respectively, under the same conditions. For UF3, the highest removal rates were 64%, 62%, and 92% for COD, BOD5, and TSS, respectively, at 2 bar and 1 m/s. Moreover, the experiments also demonstrated that an increase in TMP results in increased permeate flux and fouling resistance, while CV has also an impact on the permeate flux. Additionally, a very satisfactory retention rate for microorganisms was observed, exceeding 90%, with no presence of helminth eggs (100% removal) detected in the treated water. Nutrient elimination was also notable, with reductions of 14% for total Kjeldahl nitrogen (TKN) and 50% for total phosphorus (TP) using the UF1 membrane, which was selected based on its optimal performance.

Performance of Chitosan/Carbon Nanotube-Coated Ultrafiltration Membranes for Natural Organic Matter Removal from Drinking Water

The objective of this study is to improve the filtration efficiency of commercially available polyethersulfone (PES) ultrafiltration (UF) membranes, with a specific focus on removing natural organic matter (NOM) and preventing membrane fouling. The modification of UF membranes was accomplished by utilizing chitosan/multi-walled carbon nanotubes (CS/MWCNT-OH) and employing both dip and spin coating techniques. The membrane surface morphologies were evaluated using the Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and Energy-Dispersive X-ray Spectroscopy (EDX) techniques. Tests were carried out to assess the effectiveness of the membranes in a laboratory-scale system using two primary water sources from Istanbul, specifically the Melen River and Terkos Lake. Total organic carbon (TOC), UV254 absorbance, turbidity, and trihalomethane formation potential (THMFP) were all measured as part of a thorough analysis. The surface morphology investigations verified the effective deposition of MWCNT-OH nanoparticles onto the membrane surface. This was corroborated by the reduction in the water contact angle, showing an improvement in the hydrophilicity of the membrane. The modified membranes demonstrated much higher TOC removal rates compared to the original membranes. Specifically, the removal efficiencies for Melen River and Terkos Lake were 37.14% and 56.86%, respectively. Nevertheless, the alteration of the surface led to a decline in membrane flux as a result of the concurrent drop in pore size. To summarize, the results of this work highlights the considerable capability of surface modification using CS/MWCNT-OH to improve the performance and antifouling characteristics of commercial PES UF membranes.

Removal of Micropollutants in Water Reclamation by Membrane Filtration: Impact of Pretreatments and Adsorption.

Organic micropollutants (OMPs) present in water and wastewater are in the spotlight because of their potentially harmful effects even at low concentrations and the difficulties of their elimination in urban wastewater treatment plants (UWWTPs). This study explores the impact of some membrane filtration processes on the removal of a group of 11 OMPs with an eye on the effects of two pretreatments (i.e., coagulation and adsorption onto powdered activated carbon (PAC)) and the adsorption of OMPs onto the membranes on the overall removal. For this purpose, ultrafiltration (UF) and nanofiltration (NF) experiments were conducted with selected OMPs spiked in ultrapure water and secondary effluents from UWWTPs. It was observed that the adsorption of OMPs onto the membranes was influenced by the characteristics of the membranes, as well as the presence of effluent organic matter (EfOM). Since adsorption was the dominant mechanism for the rejection of OMPs by UF membranes, a study of the adsorption equilibrium of the micropollutants using UF membrane pieces as the adsorbent was conducted. The adsorption isotherms for the most hydrophobic OMPs fitted the Langmuir model. The efficiency of coagulation and powdered activated carbon (PAC) adsorption coupled with UF were also investigated. Both pretreatments alleviated membrane fouling and improved the rejection of organic and inorganic matter. The PAC pretreatment significantly improved the removal of OMPs in the combined PAC/UF process. The best options for achieving reclaimed water with satisfactory physicochemical quality, nearly devoid of OMPs and microorganisms, and suitable for diverse reuse purposes are either the NF treatment or the combination of PAC/UF.

Impact of membrane characteristics and chemical ageing on algal protein fouling behaviour of ultrafiltration membranes

Membrane characteristics can exacerbate the prevailing challenges associated with membrane fouling in industry. However, the combined impact of deliberate membrane modifications and the unavoidable effects of chemical ageing on fouling behaviour is still not well understood. In this study, three polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes with different pore size and surface roughness were selected and subject to chemical ageing with 5000 ppm sodium hypochlorite (NaOCl) at pH 10.5, selected to simulate accelerated ageing conditions. The impact of NaOCl on membrane characteristics was assessed for exposure times from 1.2 x 105 to 25.2 x 105 ppm·h using scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, contact angle, and clean water resistance analysis. The fouling behaviour of each pristine and aged membrane was compared using 10 mg C·L−1 dissolved organic carbon algal protein feed containing 18 % biopolymeric compounds. The membrane with intermediate pore size presented lower overall filtration resistance compared to the membrane with smaller pores that developed rapid foulant cake layers. It also displayed less susceptibility to fouling via pore blocking mechanisms compared to membranes with larger pores where greater surface area available in pore walls leads to higher foulant adhesion.

Recovery of organic nutrients from biogas slurry using decolorized ultra filtration membrane compared with nanofiltration membrane

Membrane separation technology has played a crucial role in concentrating biogas slurry (BS) for efficient water discharge. However, a membrane that selectively separates organic molecules and inorganic ions for the recovery of organic nutrients from BS for its valorization has not yet been reported. In this study, we investigated the use of decolorized ultra filtration membrane (DUFM) for the separation of organic molecules and inorganic ions from BS, compared it with the commonly used commercial nanofiltration (NF). The results showed that DUFM concentrated approximately 63 % of the COD content, which was 24 % lower than that achieved by NF. However, the concentrated BS using DUFM exhibited higher levels of protein-like substances (9 %), aromatic humic-like substances (14 %), and pigments (8 %) compared to NF, as indicated by absorbance of λ254, λ420 and λ560. In terms of inorganic ions, NH4+, Ca2+, HCO3-, and PO43- constituated approximately 88 %, 90 %, 80 %, and 70 % in the permeate side of DUFM, respectively. In constrast, NF allowed only about 70 % of NH4+ and 67 % of HCO3- to pass through, with almost complete rejection of PO43- and Ca2+. The mix-charged DUFM (500 Da) demonstrated superior separation of organic molecules and inorganic salts with low energy consumption compared to NF (150 Da) with negative charges. The DUFM with mix-charged performance increases organic molecules rejection by Donnan effect via electrostatic exclusion and with 500 Da reinforces inorganic ions’ permeation by size exclusion. Additionally, DUFM exhibited tolerance for large molecular dissolved organic matter in BS due to its membrane’s high surface hydrophilicity and smoothness. In conclusion, this study suggests DUFM, with its mix-charged characteristics, could serve as a promising membrane for the selective separation of organic molecules and inorganic ions, facilitating the recovery of organic nutrients for BS valorization.

Pre-oxidation and coagulation-flocculation as a pretreatment to UF-RO applied for surface water treatment and arsenic removal

In this paper, the effects of applying pre-oxidation, coagulation, and flocculation (C/F) as pretreatment of an ultrafiltration (UF) - reverse osmosis (RO) system treating water containing arsenic were assessed. For this, the performance of a pilot scale – with a maximum treatment capacity of 2.25 m3/h - UF-RO system with and without pretreatment was evaluated. The membranes were able to generate high-quality permeates, even when the feed presented a remarkable increase in color (>2100 uH) and turbidity (>300 NTU) due to the beginning of the rainy season. UF was not efficient for arsenic removal, so RO was essential to guarantee safe water, generating permeates with concentrations below 0.5 μg/L of arsenic. The effective removal of iron and manganese, among other ions, was verified using membranes. Given the high quality of the permeates, blend formulation strategies were carried out, mixing filtered water from the conventional water treatment plant and RO permeate (Strategy I) and mixing filtered water, UF permeate, and RO permeate (strategy II). Strategy II was viable for arsenic concentrations in filtered water of 13 and 15 μg/L. Pretreatment was important in maintaining a higher membrane permeability and ensured a more stable performance in the face of variations in feed quality, which may be seasonal in some places, as in the present case, where feed quality is significantly altered by the rainy season. Overall, although UF and RO membranes are effective processes for treating surface water containing arsenic, the results suggested that pretreatment, which is already part of the treatment of several water treatment plants, guarantees more robustness to the treatment concerning a higher and more stable membrane permeability, directly impacting operational expenses with membranes operation.

VUV coupled with low-dose H2O2 as pretreatment prior to UF: Performance, mechanisms, DBPs formation and toxicity evaluation

Ultrafiltration (UF) is widely used in drinking water plants; however, membrane fouling is unavoidable. Natural organic matter (NOM) is commonly considered as an important pollutant that causes membrane fouling. Herein, we proposed VUV/H2O2 as a UF pretreatment and used UV/H2O2 for comparison. Compared to UV/H2O2, the VUV/H2O2 system presented superior NOM removal. In the VUV/H2O2 system, the steady-state concentration of HO• was approximately twice that in the UV/H2O2 system, which was ascribed to the promoting effect of the 185 nm photons. Specifically, 185 nm photons promoted HO• generation by decomposing mainly H2O at a low H2O2 dose or by decomposing mainly H2O2 at a high H2O2 dose. The VUV/H2O2 pretreatment also demonstrated better membrane fouling mitigation performance than did UV/H2O2. An increase in the H2O2 dose promoted HO• generation, thereby enhancing the performance of NOM degradation and membrane fouling alleviation and shifting the major membrane fouling mechanism from cake filtration to standard blocking. The VUV/H2O2 (0.60 mM) pretreatment effectively reduced disinfection byproducts (DBPs) formation during chlorine disinfection. Additionally, the oxidant H2O2 affected the membrane surface morphology and performance but had no evident effect on the mechanical properties. In actual water treatment, the VUV/H2O2 pretreatment exhibited better performance than the UV/H2O2 pretreatment in easing membrane fouling, ameliorating water quality, and reducing DBPs formation and acute toxicity.

Spatiotemporal carbon footprint analysis of bottled water production by ultrafiltration and reverse osmosis

The sustainable engineering of water treatment processes is critical for reducing the environmental impact of the bottled water industry, a sector experiencing growth parallel to rising standards of living. This study focuses on the environmental footprint of two membrane processes—ultrafiltration (UF) and reverse osmosis (RO)—used in the production of bottled drinking water. By employing life cycle assessment (LCA), we compare the carbon footprints of mineral water production via UF from high-quality sources against purified water production using RO technology. Initial findings indicate minor differences in the carbon footprints for one 550-mL bottled water produced by each method. However, the incorporation of green manufacturing practices reveals a significant reduction in the carbon footprint. Specifically, our analysis shows that with the deep decarbonization of the power grid and freight electrification, the carbon footprint of mineral water can be reduced by 36.04 %. Additionally, through the adoption of renewable energy and the recycling of plastic packaging after consumption, the carbon footprint of mineral water could be lowered to 0.0295 kg CO2-eq per 550-mL bottled water, demonstrating that mineral water offers low-carbon potential. This study further explores the roles of production location, transportation, and the adoption of various decarbonization strategies in optimizing the environmental footprint of bottled water. Our findings reveal the quantitative decarbonization potential of membrane processes, coupled with sustainable practices, for bottled drinking water production, supporting the industry's shift towards greater environmental sustainability.

Synthesis and Characterization of a Modified Silica/Cellulose Acetate Nanocomposite Ultrafiltration Membrane for Phenol Removal from Wastewater

In addressing the critical environmental challenge of phenol pollution in water sources, this work studies phenol removal from wastewater using advanced ultrafiltration membranes. These membranes are enhanced with hydrophilic nanoparticles, specifically silica-based ones, to boost their efficiency and effectiveness. The process involves creating cellulose acetate (CA) mixed-matrix membranes, where silica nanoparticles are initially coated with a choline chloride-ethylene glycol deep eutectic solvent (DES). This composite is then incorporated into the CA membranes at varying concentrations of 0.25 %, 0.5 %, and 0.75 % by weight using phase inversion. The membranes are thoroughly examined for their structure and performance utilizing scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, contact angle measurements, pore size analysis, porosity assessment, and mechanical strength tests.Additionally, water flux and phenol removal performance tests were performed using a dead-end filtration setup at a pressure of 1 bar. Incorporating DES-modified nanofillers significantly enhances the membranes’ hydrophilicity and phenol removal efficiency. The internal structure exhibits a finger-like morphology with increased porosity and larger pore sizes. Notably, the membrane fabricated with 0.5 wt% modified nanoparticles showed the highest phenol removal (about 74 %) for 30 ppm aqueous phenol and water flux of 126.38 L m−2h−1. This indicates that using modified nanoparticles (DES-SiO2) in engineering ultrafiltration (UF) membranes results in an enhanced pore structure, improved chemical properties, and the effective removal of small molecules, including phenol.

Ultrafiltration and reverse osmosis integrated to conventional drinking water treatment to ensure human right to water in dam break scenarios: From bench- to pilot-scale

Previous events of tailing dam failures were associated with impacts in the water sources of drinking water treatment plants, which involves elevated concentrations of suspended solids and metal(oid)s. This study assesses the effectiveness of conventional treatment processes at a lab-scale, highlighting their limited robustness in treating water with different physicochemical qualities. Subsequently, it validates the integration of ultrafiltration (UF) and reverse osmosis (RO) into an existing water treatment plant to enhance its performance. The processes were conducted at a pilot scale, operating for 660 h under varied turbidity (<2 – 200 NTU) and contaminant (iron, manganese, and arsenic) concentrations. The membranes operated steadily with an average permeate flux of 38.6 ± 0.9 L/m2h and 19.6 ± 0.8 L/m2h for UF and RO, respectively. UF fouling was primarily related to internal pore blocking and attributed to organic matter and inorganic compounds, identified using excitation-emission matrix and energy-dispersive X-ray mapping across the cross-section of its fibers. Due to the limitations of UF in removing dissolved species, RO became necessary and ensured that all parameters analyzed met drinking water standards. The UF-RO contributes to higher robustness to conventional treatment processes and addresses operational challenges associated with a dam rupture event such as the unforeseen alteration in the quality of surface water that hinders the optimization of pre-oxidants and coagulants in conventional treatment process. To reduce costs, energy requirements, and the size of membrane-based systems, a blending strategy was proposed with a focus on achieving drinking water standards. The suggested blends include effluent from sand filters and RO permeate in a 1:1 ratio. That was only possible due to the high quality achieved for RO permeate. Apart from creating more compact systems, the blending strategy promotes the remineralization of RO permeate, mitigating undesirable characteristics such as corrosiveness, taste, and odor. For the concentrate, UF concentrate could be recycled back into the treatment process, improving water recovery in the drinking water facility, while the concentrate from RO adheres to discharge limits. Overall, the study advances investigations on integrating ultrafiltration and reverse osmosis with conventional drinking water treatment to address water quality issues from tailing dam ruptures.

Generating sustainable cement material from seawater with low-cost ultrafiltration (UF) membrane electrolysis

Membrane electrolysis offers a promising avenue for in-situ generation of hydroxide ions (OH−), facilitating the recovery of magnesium (Mg2+) and calcium (Ca2+) ions from seawater as alkaline earth hydroxide precipitates. This process paves the way for an alternative greener method in the production of raw materials for cement manufacturing compared to limestone mining. Despite its potential, the application of conventional ion migration membranes, such as anion exchange membrane (AEM) and cation exchange membrane (CEM), is hampered by their high cost and low mechanical quality, posing significant barriers to industrial scalability. In this work, we introduce the utilization of commercially available high mechanical strength ultrafiltration (UF) membrane within a two-chamber electrochemical system, repurposing it as an ion migration membrane due to its distinct advantages in terms of simplicity and relative cost-efficiency than conventional AEM. This research demonstrates that the UF membrane exhibited a comparable performance to AEM in terms of OH− production. Both membranes achieved 97–99 % removal of Mg2+ and Ca2+ within 3 h at a current density of 8 mA/cm2 and maintained comparable migration rate of SO42− ion. Compared to AEM, a notable distinction of the UF membrane is its reduced migration rate of Cl− ions, resulting in lower membrane discoloration/oxidation. Furthermore, the investigation reveals that utilizing a Na2SO4 solution as an alternative anolyte, despite being slower for OH− production, offers economic advantages and facilitates higher selective recovery of Mg2+ over Ca2+. The end products of this process, MgO and CaO, are viable raw materials for cement production, underscoring a sustainable and low carbon approach compared to conventional limestone mining of cement production.

FABRICATION AND CHARACTERIZATION OF POLYETHERSULFONE (PES) MEMBRANES BY BLENDING POLYMERS FOR REMOVAL OF ORGANIC COMPOUNDS IN AIR

The PES membrane was modified using a polymer blending method to improve the performance and characteristics of the membrane. This research aims to see the effect of adding biosilica additives on the performance characteristics of PES membranes and determine the optimal composition of additives and solvents for making membranes. The membrane was made using the Non-solvent Induced Phase Separation (NIPS) method with a composition consisting of 18% PES, with the addition of varying concentrations of silica (1%, 2%, 3%, and 4%) and the membrane using the solvent N-Methyl- 2 Pyrrolidone (NMP) and Dimethyl Sulfoxide (DMSO). Membrane characterization was carried out by observing membrane morphology using Scanning Electron Microscopy (SEM), membrane surface functional group analysis test using Fourier Tranform Infrared (FTIR), membrane porosity test using the dry-wet weight procedure method, the highest porosity value was found on membrane B2 using a solvent DMSO with 2% silica is 16.88%. Membrane performance was carried out by pure water flux testing, the highest pure water flux value was found in membrane B2 with 2% silica, namely 64.14 L/m2.h. The antifouling test uses flux ratio recovery, the highest antifouling value is found on the A3 membrane with 3% silica, namely 91.3%. As well as rejection of the humic acid solution as a Natural Organic Matter (NOM) sample model using the ultrafiltration (UF) module with a dead end filtration flow system, the highest rejection value was found on the B2 membrane with 2% silica, namely 64.4%.

Rapid pretreatment strategy to control nanofiltration membrane fouling in recycling of real textile wastewater: Comparison and mechanisms

The recycling of textile wastewater by membrane technology often necessitates intricate pretreatment steps to prevent severe membrane fouling, which lead to prolonged process-flow and elevated operation expenses. This research focuses on a two-step coagulation (TS-Co) pretreatment-nanofiltration process for treating real textile wastewater and examines its mechanism for controlling membrane fouling. The findings indicated that the removal of organic pollutants from real textile wastewater could be enhanced through first coagulation under acidic conditions, and the secondary coagulation under neutral conditions further removed the residual organics and the metal coagulants released at first stage. This synergistic effect led to chemical oxygen demand (COD) and turbidity removal efficiencies of 56.31 % and 99.29 %, respectively, which were superior to those of ultrafiltration (UF) and conventional coagulation (C-Co) pretreatment. The foulant composition and correlation analysis confirmed that protein, humic acid, and polysaccharides were the primary pollutants causing the fouling of nanofiltration membrane. Interestingly, the removal efficiency of polysaccharides using TS-Co (63.72 %) was lower than that obtained using UF (95.57 %), while the TS-Co exhibited higher removal efficiencies for humic acid and protein (97.43 % vs. 49.90 %, and 96.99 % vs. 81.07 %, respectively), indicating its excellent performance to controlling membrane fouling. Additionally, the proposed short process-flow offers cost advantages over conventional long process-flow and shows promising application prospects.

Assessment of protein and phospholipid bioaccessibility in ultrafiltered buttermilk cheese using TIM-1 in vitro gastrointestinal methods

To meet the high consumer demand, butter production has increased over the last few years. As a result, the buttermilk (BM) co-produced volumes require new ways of adding value, such as in cheese manufacturing. However, BM use in cheese milk negatively influences the cheesemaking process (e.g., altered coagulation properties) and the product’s final quality (e.g., high moisture content). The concentration of BM by ultrafiltration (UF) could potentially facilitate its use in cheese manufacturing through an increased protein content while maintaining the milk salt balance. Simultaneously, little is known about the digestion of UF BM cheese. Therefore, this study aimed to characterize the impact of UF BM on cheese manufacture, its structure, and its behavior during in vitro digestion. A 2-fold UF concentrated BM was used for cheese manufacture (skim milk [SM] – control). Compositional, textural, and microstructural analyses of cheeses were first conducted. In a second step, the cheeses were fed into an in vitro TNO gastrointestinal digestion model (TIM-1) of the stomach and small intestine and protein and phospholipid (PL) bioaccessibility was studied. The results showed that UF BM cheese significantly differed from SM cheese regarding its composition, hardness (p < 0.05) and microstructure. However, in TIM-1, UF BM and SM cheeses showed similar digestion behavior as a percentage of protein and PL intake. Despite relatively more non-digested and non-absorbed PL in the ileum efflux of UF BM cheese, the initially higher PL concentration contributes to an enhanced nutritional value compared to SM cheese. To our knowledge, this study is the first to compare the bioaccessibility of proteins and PL from UF BM and SM cheeses.

Comparison of Coagulation-Integrated Sand Filtration and Ultrafiltration for Seawater Reverse Osmosis Pretreatment.

The removal of dissolved organic matter (DOM) from seawater before the reverse osmosis (RO) processes is crucial for alleviating organic fouling of RO membranes. However, research is still insufficiently developed in the comparison of the effectiveness of integrating coagulation with ultrafiltration (UF) or sand filtration (SF) in the pretreatment stage of seawater reverse osmosis (SWRO) for the removal of DOM. In this study, we investigated the effect of pretreatment technologies on RO fouling caused by DOM in seawater, including the integration of coagulation and sand filtration (C-S pretreatment) and the integration of coagulation and ultrafiltration (C-U pretreatment). Both integrated pretreatments achieved comparable DOM removal rates (70.2% for C-U and 69.6% for C-S), and C-S exhibited enhanced removal of UV-absorbing compounds. Although C-U was more proficient in reducing the silt density index (below 2) compared to C-S (above 3) and improved the elimination of humic acid-like organics, it left a higher proportion of tyrosine-protein-like organics, soluble microbial by-product-like organics, and finer organics in the effluent, leading to the formation of a dense cake layer on RO membrane and a higher flux decline. Therefore, suitable technologies should be selected according to specific water conditions to efficiently mitigate RO membrane fouling.

Next-generation membranes for verapamil removal: Graphene oxide quantum dot-modified polyethersulfone membranes

The presence of verapamil in water sources has gained attention due to its potential risks to ecosystems and human health. Because of its great separation performance and simplicity of integration into existing treatment processes, membrane filtration could be a viable alternative. Polyethersulfone (PES) membrane is usually employed for filtration processes due to its good mechanical and thermal stability. However, pristine PES membrane exhibits low flux and lower fouling properties due to its poor antibacterial properties. Thus, the phase inversion approach was used in the current study to develop graphene oxide quantum dots (GOQDs)-modified PES ultrafiltration (UF) membranes with varying quantities of GOQDs loading (0.01–0.07 wt%). With 0.03 wt% GOQDs, the PES composite membrane exhibited a water flux of 75.23 ±10.43 L/m2 h with a verapamil retention capability of 80.36%. All the modified PES membranes containing GOQDs exhibited the formation of inhibition zones, with PES-0.07 membranes (21.00 mm) showing more pronounced zones. The incorporation of GOQDs proved to be a promising and sustainable approach for modifying PES membranes, enhancing their flux, rejection performance, and antibacterial properties, which could be beneficial in removing pharmaceutical compounds from aqueous solution.

Biodegradable ultrafiltration membrane enhanced with anti-biofouling agent from Anacardium occidentale extract

Our research focuses on developing environmentally friendly biodegradable ultrafiltration (UF) membranes for small-scale water purification in areas lacking infrastructure or during emergencies. To address biofouling challenges without resorting to harmful chemicals, we incorporate bio-based extracts, such as methyl gallate from A. occidentale leaves, a Malaysian ulam herb, known for its quorum sensing inhibition (QSI) properties. The methyl gallate enriched extract was purified by solvent partitioning and integrated into cellulose-based UF membranes (0 to 7.5% w w–1) through phase inversion technique. The resulting membranes exhibited enhanced anti-organic fouling and anti-biofouling properties, with flux recovery ratio (FRR) of 87.84 ± 2.00% against bovine serum albumin and FRRs of 76.67 ± 1.89% and 69.57 ± 1.77% against E. coli and S. aureus, respectively. The CA/MG-5 membrane showed a 224% improvement in pure water flux (PWF) compared to the neat CA membrane. Our innovative approach significantly improves PWF, presenting an environmentally friendly method for biofouling prevention in UF membrane applications.